Since a structural member of a reactor vessel is required to have corrosion resistance such as stress corrosion cracking resistance in a high-temperature and pressure water environment, a Ni-based alloy excellent in corrosion resistance, Inconel 600 (15%Cr-75%Ni) or Inconel 690 (30%Cr-60%Ni), has been used.
To further improve the corrosion resistance of these Ni-based alloys, various techniques described below have been proposed.
For example, Patent Documents 1 and 2 disclose a Ni-based alloy in which the stress corrosion cracking resistance is improved by carrying out final annealing at a regulated heating temperature and holding time after extruding and cold working Patent Document 3 discloses a Ni-based alloy in which the grain boundary damage resistance is improved by forming an amorphous alloy layer coated on the surface layer to remove grain boundaries. Patent Document 4 discloses a high-strength Ni-based alloy in which the stress corrosion cracking resistance is improved by forming a micro-structure where M23C6 is precipitated preferentially in a semi-continuous form at grain boundaries by containing at least one of a γ′ phase and a γ″ phase in a y matrix. Patent Document 5 discloses a Ni-based alloy in which the intergranular corrosion resistance, intergranular stress corrosion cracking resistance, and mechanical strength in a weld heat affected zone are improved by properly balancing the contents of components of C, N, and Nb. Patent Document 6 discloses a Ni-based alloy in which the intergranular stress corrosion cracking resistance is improved by forming a micro-structure where the low angle boundary ratio at grain boundaries is 4% or more.
Citation List
[Patent Document]
    [Patent Document 1] JP60-245773A    [Patent Document 2] JP58-67854A    [Patent Document 3] JP61-69938A    [Patent Document 4] JP62-167836A    [Patent Document 5] JP1-132731A    [Patent Document 6] JP2004-218076A